A delta motor system typically includes a delta motor, a three phase power source and a motor controller. During start up, delta motors often experience potentially damaging high inrush currents and starting torques. This can adversely effect the performance of the motor drive and increase general wear and tear leading to higher maintenance costs. In addition, current peaks during motor startup can also cause voltage disturbances in the power supply.
Motor controllers are typically used to restrict the motor torque and reduce the high starting currents by controlling the application of voltage from the three phase power source to the delta motor. The motor controller generally includes a set of three control switches that are connected between the line voltage terminals of the three phase power source and each of the windings of the delta motor. The motor controller regulates the voltage from the three phase power source to the delta motor by selectively opening and closing the three control switches. The proper operation of the delta motor is dependent on the proper regulation of the control switches.
The motor controller's internal timing mechanisms are specifically designed to regulate the application of specific line voltages from the three phase power source to specific delta motor windings based on a predesignated wiring configuration. Conventional electrical leads are typically used to connect the delta motor windings to the control switches and to the line voltage terminals. Since the electrical leads providing connection to the delta motor terminals are not always clearly marked, mistakes in wiring the delta motor system are common.
A common wiring error occurs when each of the three line voltage lines of a three phase power source have been connected to both ends of one of the three motor windings in a dead ended winding configuration. When a run command is issued to a delta motor having all of its windings in a dead ended configuration, the indicator for the motor controller will show that it is running and the indicator for the delta motor will show that the delta motor is up to speed even though the delta motor has not actually started and there is no current flowing through any of the windings.
Clearly it would be desirable to use a motor controller that automatically detects when all of the delta motor windings are dead ended. Such a motor controller would facilitate the wiring process of a delta motor system by detecting the fault condition during the installation process and result in reduced troubleshooting time and expenses. The present invention seeks to achieve these objectives.